In an existing reflective array antenna technology, a commonest reflection focusing antenna is a parabolic antenna. A spherical wave radiated by a feed disposed on a paraboloid focus becomes, after being reflected by a paraboloid, a planar wave parallel to an antenna axis, so that a field distributed on a planar antenna aperture is an in-phase field. The parabolic antenna has advantages such as a simple structure, a high gain, strong directivity, and a wide working frequency band. However, a curved parabolic reflection surface leads to a bulky and heavy antenna, which restricts an application in a space-limited occasion, for example, a spacecraft antenna. In addition, the parabolic antenna relies on a mechanically-rotated beam scanning manner, which makes it difficult to meet a flexible requirement for a beam direction.
To overcome these defects of a traditional reflection antenna, a new type of reflective array antenna is proposed in a relevant technology. The reflective array antenna uses a phase-shifting unit, for example, a dipole or a microstrip patch having a phase-shifting feature, to form a reflective array and uses a phase-shifting feature of the phase-shifting unit to construct an equivalent paraboloid. However, an overall phase-shifting effect of the reflective array antenna is not exquisite enough and a beam modulation capability for an electromagnetic wave is poor, thereby affecting bandwidth and working performance of the reflective array antenna.
In addition, in the relevant technology, the reflective array antenna is designed for a specific working frequency band. A feed location is fixed relative to a reflective array surface. Therefore, a same reflective array surface that is designed can only work for an electromagnetic wave with a specified incident angle, for example, the reflective array surface is applied to a satellite television antenna. The reflective array surface can only receive a satellite television signal in a specific region, which cannot meet a requirement that a same type of satellite television antenna covers multiple regions.
Further, in the communications field, a radiation pattern of an electromagnetic wave used as a signal carrier in space plays a very important role in signal propagation. Generally, a pattern of an electromagnetic wave exited from a signal source cannot meet a normal requirement, and modulation needs to be performed on a radiation pattern of the electromagnetic wave. Usually, an electromagnetic wave radiation pattern is modulated by using a phase modulation method, that is, a phase of an electromagnetic wave emitted from a signal source is modulated to a required phase by using a device or an apparatus. A common method of modulating a space phase of an electromagnetic wave is: using a metal reflection surface to perform phase correction; and changing, by the metal reflection surface, an existing electromagnetic wave space phase distribution by using a different appearance design of the metal reflection surface to form a target phase distribution. This method of performing, based on a metal reflection surface, space phase correction on an electromagnetic wave features a simple structure, a wide working frequency band, and a large power capacity, but highly relies on geometrical appearance. The appearance is bulky, a requirement for a production process precision is high, and costs are relatively high.
Besides, a planar array reflection surface uses a periodically arranged phase-shifting unit array to perform phase modulation. With light weight and a small volume, the planar array reflection surface does not rely on geometrical appearance in performance, is easily conformal, and is of relatively good work environment adaptability. However, a working mechanism of the planar array reflection surface is using each independent phase-shifting unit on the reflection surface to correct an existing phase distribution to a target phase distribution. Therefore, a requirement for a maximum phase-shifting range of a phase-shifting unit is relatively high.
An existing document has clearly pointed out that an initial phase of an incident electromagnetic wave can be modulated to a target phase only when a maximum phase-shifting range of a phase-shifting unit reaches at least 360 degrees, so as to obtain an expected electromagnetic wave radiation pattern. This requirement for the maximum phase-shifting range of the phase-shifting unit greatly restricts design of the planar array reflection surface. Therefore, there is a strict restriction on substrate design and phase-shifting unit design of the planar array reflection surface, thereby increasing production costs and affecting bandwidth performance of the planar array reflection surface.
Further, in a traditional reflective array theory, it is generally required that dimensions of a phase-shifting unit should be less than ½ of a wavelength of an electromagnetic wave. In a relevant technology, it is shown that, when dimensions of a phase-shifting unit are reduced from a half-wavelength to a subwavelength (⅙ of a wavelength), a phase modulation capability of an array reflection surface formed by a single layer of phase-shifting units becomes poorer and a phase-shifting range is reduced by 200 degrees. This cannot meet a requirement mainly because a gap between phase-shifting units is less than 0.001 millimeters after dimensions of a phase-shifting unit are reduced to ⅙ of a wavelength of an electromagnetic wave, which causes a grating lobe effect, thereby affecting performance of the reflective array antenna.
In this way, a requirement for unit dimensions of a phase-shifting unit greatly restricts design of the planar array reflection surface. Therefore, there is a strict restriction on substrate design and phase-shifting unit design of the planar array reflection surface, thereby increasing production costs and affecting bandwidth performance of the planar array reflection surface.
Further, owing to advantages such as a low section plane, low costs, easy conformal performance, easy integration, easy portability, and good concealment, the reflective array antenna is widely applied in a long-distance wireless transmission system such as satellite communications and deep space exploration. A reflection surface in the reflective array antenna generally uses an entire piece of sheet metal, a metallic coating, or a metallic film to implement a reflection function. If a thickness of the sheet metal, metallic coating, or metallic film is large, antenna costs increase. If the thickness of the sheet metal, metallic coating, or metallic film is reduced to decrease costs, when the thickness reaches a certain degree, for example, 0.01 to 0.03 millimeters, a length and a width of the sheet metal, metallic coating, or metallic film are far greater than the thickness of the sheet metal, metallic coating, or metallic film. In this case, warpage may easily occur due to stress in preparation and actual applications. Once warpage occurs, not only an entire antenna surface becomes unsmooth, but also electrical performance of the reflective array antenna is seriously affected and even a signal cannot be received or sent. On one hand, a yield in a product preparation process is decreased, thereby causing a lot of waste. On the other hand, maintenance costs after a product is used are also increased.
Further, the reflective array antenna usually includes a medium slab, multiple unit structures disposed on the medium slab, and a reflection layer disposed on another side of the medium slab. In an existing reflective array antenna, a reflection layer or multiple unit structures are attached to two sides of a medium slab by means of copper etching or attached to two sides of a medium slab by means of hot pressing. When a reflective array antenna prepared in the foregoing manner is applied, the following problem exists: a medium slab and reflection layer of the reflective array antenna may generate an effect of thermal expansion and contraction under a temperature difference between day and night and a temperature difference between different regions. Because a contraction percentage of the medium slab is different from a contraction percentage of a reflection surface and thicknesses of a unit structure and the reflection layer are relatively thin, thermal expansion and contraction of the medium slab and reflection surface causes warpage on a relatively thin unit structure and/or the reflection layer. A warped unit structure and/or reflection layer affects a response of the reflective array antenna to an electromagnetic wave and also increases maintenance costs.